Blood is a suspension of particulates (e.g., red blood cells and white blood cells) that is routinely examined for the presence of abnormal organisms or cells, such as cancer cells, ova, parasites, microorganisms, and inflammatory cells. Blood is typically analyzed by smearing a sample on a slide and is stained and visually studied usually by bright field microscopy, and then, if needed, by immunologic stains and/or other molecular techniques. Visual detection of cancer cells and other abnormal organisms in smears is often hindered by the presence of extraneous material interspersed between cells. Additionally, standard smear preparations utilize only a fraction of the sample since the smears must be thin enough to allow the passage of light, but the examination of an entire blood sample across multiple smears is often impractical and cost prohibitive in most laboratory settings. Consequently, the sensitivity of disease detection can be limited by the smear methodology.
Blood samples can also be collected to detect a variety of different viruses. For example, HIV, cytomegalovirus, hepatitis C virus, and Epstein-Barr virus can be detected in blood samples using polymerase chain reaction (“PCR”)-based or serologic tests. Although PCR-based tests are sensitive and quantitative, PCR-based tests can be cost prohibitive and imprecise because they may detect contaminants or other cross-reacting sequences in the blood sample. Serology on the other hand can also be used to detect the presence of certain viruses, but serology does not provide quantitative information, such as how much of a virus is present?
Practitioners, researchers, those working with suspensions continue to seek systems and methods for accurately analyzing suspensions for the presence or absence of various kinds of particulates.